# How to calculate tortuosity of a coastline?

I would like to calculate the tortuosity (or fractal dimension) of a coastline within a 1km buffer surrounding a point on that coastline. I have hundreds of points and therefore need a tool or scripts that will do the calculation on a mass scale. Can someone help me please?

I am using ArcMap10

-

Hawth's Tools used to have a Line Metrics tool which would calculate the sinuosity. However, Hawth's tools was discontinued when ArcGIS 10 came out. It's now called the Geospatial Modelling Environment. Unfortunately, in section 5.2 (page 151) of this document, it states that the functionality is not currently available.

However, if you look at the picture which was linked to the original tool, there are instructions for how to calculate it. It shouldn't be too difficult to calculate yourself.

You say that your data is in points. You will first need to convert your points to a polyline. You can do this in ArcGIS as well in the Geospatial Modelling Environment.

You'll then want to split your polyline into line segments. You can do that with ET GeoWizard's Split Polyline Tool.

Hopefully, this will work out for you.

Update

Just realised that the Split Polyline Tool is not a free function. Of course, you can always "Explode" the polyline in edit mode in ArcGIS.

-

If you would like a raster layer that represents fractal dimension for every point (cell center) of your coastal landscape within 1km radius, perhaps try Fragstats 4.1 - it has the ability to output a grid calculated as a 'Local structure gradient' from a moving window that you specify as 'Round, with a radius of 1000.0 m' (class and/or landscape metrics).

You will need a raster version of your coastline for input. Once the Fragstats output is complete, use the Extract Values to Points to get the values in the points file attribute table - the moving window analyses simulates a 'buffer' for every cell center of the raster.

However, this approach is not as accurate as a vector method and may include parts of a complex coastline within the 1km radius that aren't contiguous with coastline immediately adjacent to the 'buffered' point.

-